[llvm-branch-commits] [llvm] release/22.x: x86: fix musttail sibcall miscompilation (#168956) (PR #176470)

[Reid Kleckner via llvm-branch-commits]

rnk wrote:

This is a longstanding serious correctness issue in x86 musttail and guaranteed TCO. I reviewed it, I think it's low risk, most of the code affected by this change is already broken, so we should merge it to LLVM 22. This will enable Rust `become` to ship and be functional sooner. 

cc @folkertdev @efriedma-quic @phoebewang 

https://github.com/llvm/llvm-project/pull/176470